La boheme English National Opera, Coliseum, London WC2, Wed to 30 March

For so vast a country, with such boundless potential, Russia has cornered the market in little more than self-pity. When not being menaced by foreigners, it has tended to go in for murderous self-destruction, as much under the tsars as their communist successors. This has in turn produced a stream of great art, literature and music, bewailing the nation's self-inflicted wounds, invariably at a length befitting the scale of the carnage.

After Boris Godunov, his epic setting of Pushkin's drama charting the anarchic pre-Romanov interregnum, Modest Mussorgsky spent his last years composing Khovanshchina, an anguished saga of aristocratic, religious and paramilitary intrigue during Peter the Great's enlightened, turn-of-the-18th-century reformation. The outmoded warlords, as in the eponymous Khovanskys, are at loggerheads with both Golytsin's discredited liberals and Dosifei's religious fundamentalists, known as the 'Old Believers'. It cannot, nor will it, come to good.

The only winner is always going to be the Tsar, who never appears on stage. The dissolute Khovansky senior is idly assassinated while his hedonist son joins the climactic mass suicide of the cult-like 'Old Believers' - along with his lover Marfa, whose fluctuating fortunes add some token human interest to the earnest political debate. Summing up the national mood, amid the civil bloodbath, is the trademark lament of the boyar Shaklovity for the eternal sufferings of his mother country.

Over almost four hours, the colour-coding of the various factions offers a much-needed visual aid through David Pountney's handsome, intelligent new production for Welsh National Opera. This is an ambitious, often magnificent work; but its sheer length and largely inert plot (libretto by the composer - always a mistake) inevitably lead to longueurs.

Because of its discursive nature, moreover, Pountney opts for an English translation, which is too often inaudible. As an implacable opponent of surtitles - calling them 'a celluloid condom' when they were introduced at his former base, ENO - he leaves the audience at the mercy of the declining standards of operatic diction in this country.

While some soloists are exemplary, notably Peter Hoare's Golitsyn, Peter Sidhorn's Shaklovity and Tom Randle's Khovansky fils, Robert Hayward's Khovansky père is decidedly patchy and Rosalind Plowright's Marfa yet more so. The chorus seize their chances with distinction, and Lothar Koenigs maintains much-needed momentum in the pit. But unless you do your homework in advance, which should never be necessary, you won't have the slightest clue what is going on.

Which is a shame, for Pountney is on top theatrical form. Spurning the temptation to draw easy parallels with contemporary Russia, he sets the work in the 1920s, as in Johan Engels's constructivist sets, with Marie-Jeanne Lecca's costumes symbolically leaving the belligerent toffs in the early 17th century and the Old Believers as mid-19th-century Pan-Slavists.

There is a quintessentially Pountney-esque moment in the fourth act, when Khovansky is stabbed in his bath after enjoying an exotically naked Dance of the Persian Slave. Otherwise this director for once reins himself in, to the point where the self-immolation scene is profoundly affecting - complete with Stravinsky's elegant coda to the Shostakovich version of an epic unfinished at Mussorgsky's death. This is a rare chance to see a masterwork performed in high style. But mug up before you go.

There's no need for any such preparation before English National Opera's La boheme, in the sixth revival of the 1993 staging by Steven Pimlott, who died this month aged 53. Before the first-night curtain, National Theatre director Nicholas Hytner delivered an eloquent tribute to the friend and colleague with whom he worked at ENO in the late 1970s, and to whose memory this revival is dedicated.

Restaged by Ian Rutherford, Pimlott's clean-limbed modern-dress staging moves as urgently as ever, thanks to its clever use of just one adaptable set (Tobias Hoheisel) and the management's merciful decision to rein in the bar proceeds to just one interval. The star of the show, for once, is Mark Stone's Marcello, whose ringing baritone fills the cavernous Coliseum with much more conviction than Peter Auty's timid Rodolfo or Mary Plazas's dainty Mimi. There is a raunchy Musetta from Giselle Allen and a suave double-act from Robert Poulton as Benoit and Alcindoro.

The supporting parts are also well cast, with Iain Paterson's staunch Schaunard and Matthew Rose's resonant Colline contributing to a polished ensemble feel even on the first night. But the revelation is the passionate conducting of the Chinese maestra Xian Zhang, whose ENO debut will one day be remembered as a significant stepping stone in an illustrious career.